private void onDispose() {
if (control == null) return;
this.Release();
if (controlListener != null) {
control.removeListener(SWT.Dispose, controlListener);
control.removeListener(SWT.DragDetect, controlListener);
}
controlListener = null;
control.setData(DND.DRAG_SOURCE_KEY, null);
control = null;
transferAgents = null;
}
/**
* Creates a new <code>DragSource</code> to handle dragging from the specified <code>Control
* </code>. Creating an instance of a DragSource may cause system resources to be allocated
* depending on the platform. It is therefore mandatory that the DragSource instance be disposed
* when no longer required.
*
* @param control the <code>Control</code> that the user clicks on to initiate the drag
* @param style the bitwise OR'ing of allowed operations; this may be a combination of any of
* DND.DROP_NONE, DND.DROP_COPY, DND.DROP_MOVE, DND.DROP_LINK
* @exception SWTException
* <ul>
* <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the parent
* <li>ERROR_INVALID_SUBCLASS - if this class is not an allowed subclass
* </ul>
*
* @exception SWTError
* <ul>
* <li>ERROR_CANNOT_INIT_DRAG - unable to initiate drag source; this will occur if more than
* one drag source is created for a control or if the operating system will not allow
* the creation of the drag source
* </ul>
* <p>NOTE: ERROR_CANNOT_INIT_DRAG should be an SWTException, since it is a recoverable error,
* but can not be changed due to backward compatibility.
* @see Widget#dispose
* @see DragSource#checkSubclass
* @see DND#DROP_NONE
* @see DND#DROP_COPY
* @see DND#DROP_MOVE
* @see DND#DROP_LINK
*/
public DragSource(Control control, int style) {
super(control, checkStyle(style));
this.control = control;
if (control.getData(DND.DRAG_SOURCE_KEY) != null) {
DND.error(DND.ERROR_CANNOT_INIT_DRAG);
}
control.setData(DND.DRAG_SOURCE_KEY, this);
createCOMInterfaces();
this.AddRef();
controlListener =
new Listener() {
public void handleEvent(Event event) {
if (event.type == SWT.Dispose) {
if (!DragSource.this.isDisposed()) {
DragSource.this.dispose();
}
}
if (event.type == SWT.DragDetect) {
if (!DragSource.this.isDisposed()) {
DragSource.this.drag(event);
}
}
}
};
control.addListener(SWT.Dispose, controlListener);
control.addListener(SWT.DragDetect, controlListener);
this.addListener(
SWT.Dispose,
new Listener() {
public void handleEvent(Event e) {
DragSource.this.onDispose();
}
});
Object effect = control.getData(DEFAULT_DRAG_SOURCE_EFFECT);
if (effect instanceof DragSourceEffect) {
dragEffect = (DragSourceEffect) effect;
} else if (control instanceof Tree) {
dragEffect = new TreeDragSourceEffect((Tree) control);
} else if (control instanceof Table) {
dragEffect = new TableDragSourceEffect((Table) control);
}
}